Deathloop - HDR Optimized Settings (Patreon)

The game DOES USE/APPLY Xbox & Playstation HDR Calibration app settings.

Deathloop has a good but cumbersome HDR implementation. While it supports and applies the system HDR calibration settings it still offers in-game HDR adjustments including Peak HDR Luminance control, which will have separate and unwanted effects:

The problem is that the in-game HDR settings don't reflect system HDR Calibration values as soon as you will touch anything in it (and you're inclined to do so as "Screen Luminance" setting at 300 nits only by default is bad on paper) but you will entirely lose the applied system HDR settings when you do so.

So basically, once you've setup the Xbox/Playstation HDR calibration, just click the "Reset to the Default Settings" button in-game (under the Visuals section) to be sure that the system HDR settings will be correctly applied to the game and you're good to go!

Leave "Middle Grey" , "Brightness" and "Saturation" sliders to their Defaults as those already correspond to a balanced/correct exposure, gamma and saturation.

If you still find the game too dim/dark for your taste, you can try increasing the Brightness value to 25.